Optical encoder systems, devices and methods

ABSTRACT

Disclosed are various embodiments of high-speed, high-performance, low-noise optical encoders having various means for preventing undesired stray light from reaching light detectors incorporated therein. Structures employed to block stray light in the optical encoders include light barriers, air gap trenches, and coatings disposed between first and second sides of a substrate of the encoder. Also disclosed are compact single track optical encoders having a single dome lens disposed thereover, and dual track triple dome lens optical encoders. Methods of making such optical encoders are also disclosed.

RELATED APPLICATION

This patent application is a divisional application of parent U.S.patent application Ser. No. 12/343,468 filed Dec. 23, 2008 entitled“Optical Encoder Systems, Devices and Methods ” to Yee Loong Chin etal., and claims priority and other benefits therefrom. The foregoing'468 patent application is hereby incorporated by reference herein, inits entirety.

FIELD OF THE INVENTION

Various embodiments of the invention described herein relate to thefield of optical encoders, and components, devices, systems and methodsassociated therewith.

BACKGROUND

Optical encoders are typically employed as motion detectors inapplications such as closed-loop feedback control in a motor controlsystem. Many optical encoders are configured to translate rotary motionor linear motion into a two-channel digital output for positionencoding.

Many optical encoders employ an LED as a light source. In transmissiveencoders, the light is collimated into a parallel beam by means of alens located over the LED. Opposite the emitter is a light detector thattypically consists of photo-diode arrays and a signal processor. When acode scale such as a code wheel or code strip moves between the lightemitter and light detector, the light beam is interrupted by a patternof bars and spaces disposed on the code scale. Similarly, in reflectiveor imaging encoders, the lens over an LED focuses light onto the codescale. Light is either reflected or not reflected back to the lensdisposed over the photo-detector. As the code scale moves, analternating pattern of light and dark patterns corresponding to the barsand spaces falls upon the photodiodes. The photodiodes detect thesepatterns and corresponding outputs are processed by the signal processorto produce digital waveforms. Such encoder outputs are used to provideinformation about position, velocity and acceleration of a motor, by wayof example.

Transmissive optical encoders typically generate code scale imageshaving good contrast, and hence are capable of operating at high speedswith high resolution. The high contrast characteristic of mosttransmissive optical encoders also permits the outputs provided therebyto be easily interpolated to higher resolution. Transmissive opticalencoders usually require that light emitters be placed opposite lightdetectors, and thus require a relatively high profile in respect ofpackage design.

In reflective optical encoders, the light emitter and light detectoroften may be placed on the same substrate, and thus low profile designs,fewer materials and shorter assembly times may be realized. Reflectiveoptical encoders typically suffer from low contrast, which in turn leadsto low speeds and low resolution.

Imaging optical encoders feature many of the same advantages asreflective optical encoders, such as low profiles and cost, but alsorequire diffusive code wheels. In addition, imaging optical encoderssuffer from low diffusive reflectance and usually cannot operate at veryhigh speeds.

Reflective optical encoders known in the art often suffer from severalperformance and application problems, such as stray light originating atthe light emitter hitting the light detector directly, which can causecontrast degradation, lower encoder performance, and limit resolution.Known reflective optical encoders also typically comprise oneencapsulated dome with an emitter-detector pair disposed therewithin,which often leads to poor light collimation and consequent limits onencoder performance and resolution. Known reflective encoders alsotypically feature limited encoding capability, such as a maximum of twochannels of data encoding, or a single index channel.

Various patents containing subject matter relating directly orindirectly to the field of the present invention include but are notlimited to, the following:

U.S. Pat. No. 4,451,731 to Leonard, May 29, 1984;

U.S. Pat. No. 7,182,248 to Foo et al., Jun. 10, 2008;

U.S. Pat. No. 7,385,178 to Ng et al., Nov. 11, 2008.

U.S. Pat. No. 7,400,269 to Wong et al., Jul. 15, 2008;

U.S. Pat. No. 7,394,061 to Saidan et al., Jul. 1, 2008;

U.S. Patent Publication No. 2006/0237540 to Saxena et al., Oct. 26,2006, and

U.S. Pat. No. 2008/0024797 to Otsuka et al., Jan. 21 2008.

The dates of the foregoing publications may correspond to any one ofpriority dates, filing dates, publication dates and issue dates. Listingof the above patents and patent applications in this background sectionis not, and shall not be construed as, an admission by the applicants ortheir counsel that one or more publications from the above listconstitutes prior art in respect of the applicant's various inventions.All printed publications and patents referenced herein are herebyincorporated by referenced herein, each in its respective entirety.

Upon having read and understood the Summary, Detailed Description andClaims set forth below, those skilled in the art will appreciate that atleast some of the systems, devices, components and methods disclosed inthe printed publications listed herein may be modified advantageously inaccordance with the teachings of the various embodiments of the presentinvention.

SUMMARY

In some embodiments, there is provided a single dome lens reflectiveoptical encoder comprising a substrate having a top surface withopposing first and second sides, a light emitter mounted on or attachedto the first side and configured to emit light therefrom, a single tracklight detector mounted on or attached to the second side, the singletrack light detector comprising at least one data channel light detectorand an index channel light detector, the data and index channels beingarranged along a common axis, and a single dome lens comprising anoptically transparent material, the single dome lens being formed overand in direct contact with the light emitter and the single track lightdetector such that no air gap is located between the light emitter andthe dome or the light detector and the dome. The single dome lens isconfigured to permit light emitted from the light source to be refractedthrough portions thereof for reflection from a code scale comprisingindex and data strips that are configured to travel along the commonaxis. The code scale is located operably in respect of the single domelens such that at least a portion of the light reflected from the codescale is directed towards the single dome lens and refracted throughportions thereof for detection by the light detector.

In other embodiments, there is provided a method of making a single domelens reflective optical encoder comprising providing a substrate havinga top surface with opposing first and second sides, attaching a lightemitter to the first side, the light emitter being configured to emitlight therefrom, attaching a single track light detector to the secondside, the single track light detector comprising at least one datachannel light detector and an index channel light detector, the data andindex channels being arranged along a common axis, attaching to thesubstrate an optically opaque light barrier between the light emitterand the first side and the single track light detector and the secondside, the light barrier being configured to prevent or inhibit directlight rays emitted by the light emitter from impinging directly upon thesingle track light detector, and forming a single dome lens comprisingan optically transparent material over and in direct contact with thelight emitter and the single track light detector such that no air gapis located between the light emitter and the dome or the light detectorand the dome. The single dome lens is configured to permit light emittedfrom the light source to be refracted through portions thereof forreflection from a code scale comprising index and data strips that areconfigured to travel along the common axis, the code scale being locatedoperably in respect of the single dome lens such that at least a portionof the light reflected from the code scale is directed towards thesingle dome lens and refracted through portions thereof for detection bythe light detector.

In still other embodiments, there is provided a triple dome lensreflective optical encoder comprising a substrate having a top surfacewith opposing first and second sides defined by a first axis disposedtherebetween, and opposing third and fourth sides defined by a secondaxis disposed therebetween, the first axis being substantiallyperpendicular to the second axis, a light emitter mounted on or attachedto the first side and configured to emit light therefrom, the lightemitter being covered by a first dome lens formed thereover and indirect contact therewith such that no air gap is located between thelight emitter and the first dome lens, an index channel detector mountedon or attached to a first area defined by a first overlap of the secondand third sides, the index channel detector being covered by a seconddome lens formed thereover and in direct contact therewith such that noair gap is located between the index channel detector and the seconddome lens, at least one data channel detector mounted on or attached toa second area defined by a second overlap of the second and fourthsides, the data channel detector being covered by a third dome lensformed thereover and in direct contact therewith such that no air gap islocated between the data channel detector and the second dome lens. Thefirst dome lens is configured to permit light emitted from the lightsource to be refracted through portions thereof for reflection from afirst code scale comprising data strips as well as for reflection from asecond index scale, the first code scale and the index scale beingconfigured to travel along respective parallel third and fourth axes,the index scale being located operably in respect of the first andsecond dome lenses such that at least a portion of the light reflectedfrom the index scale is directed towards the second dome lens andrefracted through portions thereof for detection by the index channeldetector, the code scale or code wheel being located operably in respectof the first and third dome lenses such that at least a portion of thelight reflected from the code scale is directed towards the third domelens and refracted through portions thereof for detection by the datachannel detector.

Further embodiments are disclosed herein or will become apparent tothose skilled in the art after having read and understood thespecification and drawings hereof.

BRIEF DESCRIPTION OF THE DRAWINGS

Different aspects of the various embodiments of the invention willbecome apparent from the following specification, drawings and claims inwhich:

FIG. 1 shows top plan and cross-sectional views of one embodiment of asingle dome lens optical encoder of the invention;

FIG. 2 shows illustrative output signals provided by the embodiment ofFIG. 1;

FIG. 3 shows top plan Wand cross-sectional views of another embodimentof a single dome lens optical encoder of the invention;

FIG. 4 shows top plan and cross-sectional views of yet anotherembodiment of a single dome lens optical encoder of the invention;

FIG. 5 a shows top plan and cross-sectional views of still anotherembodiment of a single dome lens optical encoder of the invention;

FIGS. 5 b-5 d shows cross-sectional views of various embodiments ofsingle dome lens optical encoders of the invention;

FIG. 6 a shows top plan and cross-sectional views of one embodiment of atriple dome lens optical encoder of the invention;

FIGS. 6 b-6 e show cross-sectional views of various other embodiments oftriple dome lens optical encoders of the invention;

FIG. 7 a shows a top plan view of another embodiment of a triple domelens optical encoder of the invention, and

FIGS. 7 b-7 d show cross-sectional views of various other embodiments oftriple dome lens optical encoders of the invention.

The drawings are not necessarily to scale. Like numbers refer to likeparts or steps throughout the drawings, unless otherwise noted.

DETAILED DESCRIPTIONS OF SOME PREFERRED EMBODIMENTS

In various embodiments of the invention, single and triple dome single-and dual-track optical reflective encoder systems, devices and methods,are provided.

FIG. 1 shows top plan and cross-sectional views of one embodiment of asingle dome lens optical encoder 10 of the invention. Substrate 40 has atop surface 41 with opposing first and second sides 56 and 58. Lightemitter die 42 comprises light emitter 44 (which is configured to emitlight therefrom), and is located on a first side 56 of substrate 40.Single track light detector 48 is mounted on or attached to a secondside 58 of substrate 40, and comprises at least one data channel lightdetector 24 and an index channel light detector 20.

As employed herein, the term “single track encoder” means an opticalencoder having a single code scale having data or code patterns or barsformed or presented thereon or therein, as well as index patterns orbars formed or presented thereon or therein, where the data and indexpatterns travel together along a common single axis in a single trackdisposed over a corresponding single track comprising data channel andindex channel light detectors.

The first side 56 is opposite the second side 58 on the top surface 41of substrate 40 such that light emitted from light emitter 42/44 travelsprimarily from the first side 56 upwardly towards code scale 30 forreflection therefrom downwardly towards second side 58 for detection bylight detector 46/48. In a preferred embodiment, and as shown in FIG. 1,single dome lens 50 comprises a curved outer lens surface 54 which isshaped and configured to direct light rays 43 and 47 away from lightemitter 42/44 towards code and index scale 30 and thence back to lightdetector 46/48. Note that as employed herein, the term “code scale” or“code and index scale” can mean a code wheel, a code strip, a code andindex wheel, or a code and index strip. Data channel light detector 24and index channel light detector 20 are arranged along a common axis 27,which coincides with the direction of movement of code and index scale30 disposed operably thereabove.

Continuing to refer to FIG. 1, single dome lens 50 comprises anoptically transparent material, which in a preferred embodiment is amoldable epoxy. Single dome lens 50 is formed over and in direct contactwith the light emitter 42/44 and single track light detector 48 suchthat no air gap is located between light emitter 42/44 and dome 50, orbetween the light detector 48 and the dome 50. The single dome lens 50is configured to permit light 43 emitted from the light source to berefracted through portions thereof for reflection from a code and indexscale 30 comprising index strips 31 and data strips 33, which isconfigured to travel along the common axis 27. The code and index scale30 is located operably in respect of the single dome lens 50 such thatat least a portion of the its light 47 reflected from the code and indexscale 30 is directed downwardly towards the single dome lens 50 andrefracted through portions thereof for detection by the light detector46/48. Note that the upper or outer surface 54 of single dome lens 50may have a spherical, aspherical or biconic profile above one or both ofthe emitter 42/44 and the detector 46/48.

As further shown in FIG. 1, light detector 48 may comprise a single die46 upon which the index channel and data channel light detectors areformed, or alternatively may comprise discrete dice for the indexchannel light detector and the data channel light detector,respectively. Reflective surfaces 32 formed on the underside of indexstrips 31 and data strips 33 are configured to permit upwardlyprojecting light rays 43 to be reflected therefrom to form downwardlyprojecting light rays 47.

Optional bevel or shoulder 52 may be formed around the outer peripheryof single dome lens 50. Alternatively, the outer periphery of singledome lens 50 may be configured to project upwardly from the peripheryabove the uppermost portion of single dome lens 50 so as to form aprotective protrusion to provide a protective ring or shouldertherearound.

Continuing to refer to FIG. 1, the data channel light detector 24 maycomprise one light detector, at least two light detectors correspondingto A and A\ data channels, as is known in the art, at least four lightdetectors corresponding to A, B, A\ and B\ data channels, or any othernumber of light detectors suitable for the particular application athand. In the embodiment shown in FIG. 1, four separate light detectorsform data channel light detector 24. By way of example, substrate 40 maybe a printed circuit board, a lead frame, comprise plastic or be formedfrom a suitable polymer.

FIG. 2 shows illustrative output signals provided by the embodiment ofthe optical encoder shown in FIG. 1. As shown in FIG. 2, the indexchannel provides an output signal 21 which is preferably shorter induration than the output pulses 23 a and 23 b provided by the A and Bdata channels.

FIG. 3 shows top plan and cross-sectional views of another embodiment ofsingle dome lens reflective optical encoder 10, where a portion 74 ofthe outer surface 54 of the single lens dome 50 is coated or treated toprevent or inhibit stray light rays from impinging upon the single tracklight detector 46/48. By way of example, stray or undesired light rayscan include light rays internally reflected within single dome lens 50,light rays scattered or diffused within single dome lens 50, out-of-linelight rays reflected from or scattered or diffused by code scale 30 orany other portion of optical encoder 10 or another device or component.Portion 74 of lens 50 may be formed, for example, by means of laserablation, mechanical abrasion, or by disposing an appropriate opticallyabsorptive or diffusive coating or material on the outer surface of lens50. Other means known to those skilled in the art for forming anoptically diffusive or absorptive portion over the top-most portion oflens 50 so as to shield the light detector 46/48 from scattered,out-of-line or otherwise undesired light rays are also contemplated andmay be employed.

FIG. 4 shows top plan and cross-sectional views of yet anotherembodiment of single dome lens reflective optical encoder 10, whichcomprises an optically opaque light barrier 70 disposed between thelight emitter 42/44 and the first side 56 on the one hand, and thesingle track light detector 46/48 and the second side 58 on the otherhand. The light barrier 70 is configured to prevent or inhibit straylight rays from impinging upon the single track light detector 46/48.The embodiment shown in FIG. 4 permits the performance of opticalencoder 10 to be improved in respect of prior art devices. Normally theperformance of an optical encoder is affected by stray light originatingfrom the light emitter 42/44 that propagates directly to the detector46/48, or is reflected internally, scattered or diffused within lens 50or by another device or component, that subsequently impinges upon thedetector. The light barrier 70 prevents undesired cross-talk between thelight emitter 42/44 and the light detector 46/48 from occurring. Aprincipal source of such cross-talk is light reflecting off the internalsurface defined by the upper surface 54 of lens 50 back onto detector46/48. Stray light reduces the image contrast of the encoder, and limitsthe speed or frequency that can be attained. High performance opticalencoders are able to achieve high levels of image contrast andresolution. By incorporating the light barrier 70 into the opticalencoder 10, a higher performance optical encoder can be provided. Thelight barrier 70 blocks to a significant degree undesired stray lightfrom impinging upon the light detector 46/48. As a result, the noiselevel of optical encoder 10 is minimized.

Continuing to refer to FIG. 4, according to one embodiment a method ofmaking single dome lens reflective optical encoder 10 is also provided.Substrate 40 having a top surface 41 with opposing first and secondsides 56 and 58 is provided or formed. Light emitter 42/44 is attachedto the first side 56 of the top surface 41 of substrate 40, and singletrack light detector 46/48 is attached to the second side 58 of the topsurface 41 such that the data and index channel detectors 20 and 24 arearranged along the common axis 27. The optically opaque light barrier 70is formed between the light emitter 42/44 and the first side 56 on theone hand, and the single track light detector 46/48 and the second side58 on the other hand.

Single dome lens 50 is formed over light emitter 42/44, light barrier 70and light detector 46/48. Single dome lens 50 comprises an opticallytransparent material that is disposed over and in direct contact withthe light emitter 42/44 and the single track light detector 46/48 suchthat no air gap is located between the light emitter 42/44 and the dome50, and the light detector 46/48 and the dome 50. The single dome lens50 is configured to permit light emitted from the light source 42/44 tobe refracted through portions thereof for reflection from the code scale30 comprising index strip 31 and data strips 33 that is configured totravel along the common axis 27.

In one method, the light barrier 70 is formed by transfer molding orinsert molding. In transfer molding, the light barrier 70 is transfermolded onto substrate 40, which may be a printed circuit board, a leadframe, or the like. The light barrier 70 is preferably formed from anoptically opaque, optically absorptive, optically diffusive or opticallyscattering material so as to block or redirect unwanted light. Aftertransfer molding the light barrier 70 to substrate 40, die attachmentand wire bonding steps are undertaken. Finally, the assembled substrate40 having the light barrier 70 and dices 42 and 46 attached thereto anddisposed thereon is placed in a mold tool and single dome lens 50 isformed thereover, preferably also using a transfer molding process.

In another method, light barrier 70 is formed by insert molding sameusing a high temperature plastic, and the light barrier 70 is manuallyplaced onto the substrate 40, In a variation on such a method oftransfer molding the light barrier 70, multiple cavity plastic moldedlight barriers are manually placed in the transfer mold tool or directlyupon substrates 40 according to the particular mold tool and substratedesign being employed before transfer molding single dome lenses 50. T\oprovide increased accuracy and control, the light barrier 70 can bedirectly insert molded onto the substrate 40. Before transfer moldingsteps are undertaken, however, the dice 42 and 46 are attached to thesubstrate 40 and wire bonding is carried out. Then, the light barrier 70is attached to the substrate 40 or inserted into the mold tool,depending on the particular molding tool and process design that isbeing employed. Transfer molding is next preferably employed to form thesingle dome lens 50 and encapsulate the dices 42 and 46 and the lightbarrier 70.

FIG. 5 a shows top plan and cross-sectional views of still anotherembodiment of single dome lens reflective optical encoder 10. Singledome lens reflective optical encoder 10 comprises an air gap trench 72disposed between the light emitter 42/44 and the first side 56 on theone hand, and the single track light detector 46/48 and the second side58 on the other hand. The air gap trench 72 is configured to prevent orinhibit direct light rays emitted by the light emitter 42/44 fromimpinging directly upon the single track light detector 46/48. FIG. 5 bshows a cross-sectional view of an alternative embodiment of a singledome lens optical encoder 10 having an air gap trench 72.

FIGS. 5 c and 5 d show cross-sectional views of still other embodimentsof single dome lens optical encoders 10 having air gap trench 72disposed in single dome lenses 50. In the embodiments of FIGS. 5 c and 5d, portions 74 are disposed on the outer surfaces of air gap trench 72,which are coated or treated to prevent or inhibit stray light rays fromimpinging upon the single track light detector 46/48. Portion 74 of lens50 may be formed, for example, by means of laser ablation, mechanicalabrasion, or by disposing an appropriate optically absorptive, diffusiveor scattering coating or other material on the outer surface of lens 50.Other means known to those skilled in the art for forming an opticallyabsorptive, diffusive or scattering portion 74 over the outer surfacesof air gap trench 72 so as to shield the light detector 46/48 fromscattered, out-of-line or otherwise undesired light rays are alsocontemplated and may be employed. Air gap trench 72 may be formed bymolding, grinding, ablation, and other methods known to those skilled inthe art.

Referring now to FIGS. 1 through 5 d, it will be seen that the singledome lens optical encoders 10 illustrated therein can be adapted for usein Incremental optical encoders having two, three or more data channels,commutation optical encoders having six or some other number ofchannels, pseudo absolute optical encoders, and absolute opticalencoders. In addition, the single dome lens optical encoders illustratedin FIGS. 1 through 5 d are particularly well adapted forminiaturization, as the light emitter 42/44 and the single-track lightdetector 46/48 can be placed in close proximity to one another whilestill permitting stray light to be minimized or substantiallyeliminated. The embodiments illustrated in FIGS. 1 through 5 d permitsmall optical encoder packages 10 to be constructed which share the samelens 50 for transmitting and receiving light. Improved performance alsoresults, as the noise level of the encoder 10 caused by stray lightimpinging upon the detector is minimized or eliminated. Hence, theencoder 10 can be used in high speed rotary or linear systems. Moreover,minimal investments in manufacturing processes and equipment arerequired to implement low cost transfer molding processes, which arecommonly employed in many semiconductor package encapsulationapplications.

Referring now to FIG. 6 a, there are shown top plan and cross-sectionalviews of one embodiment of a triple dome lens dual track optical encoder15. The triple dome lens reflective optical encoder 15 comprises asubstrate 40 having a top surface 41 with opposing first side 56 andsecond side 58 separated by a first axis 57 disposed therebetween.Opposing third side 57 and fourth side 59 are separated by a second axis83 disposed therebetween, where the first axis 57 is substantiallyperpendicular to the second axis 83.

Continuing to refer to FIG. 6 a, a light emitter 42/44 is mounted on orattached to the first side 56 and configured to emit light therefrom.The light emitter 42/44 is covered by a first dome lens 60 a formedthereover and in direct contact therewith such that no air gap islocated between the light emitter 42/44 and the first dome lens 60 a. Anindex channel detector 20/46 b is mounted on or attached to a first areadefined by a first overlap of the second and third sides 58 and 57. Theindex channel detector 20/46 b is covered by a second dome lens 60 bformed over and in direct contact therewith such that no air gap islocated between the index channel detector 20/46 b and the second domelens 46 b.

At least one data channel detector 24/46 c is mounted on or attached toa second area defined by a second overlap of the second and fourth sides58 and 59. The data channel detector 24/46 c is covered by a third domelens 60 c formed over and in direct contact therewith such that no airgap is located between the data channel detector 24/46 c and the thirddome lens 60 c.

The first dome lens 60 a is configured to permit light emitted from thelight emitter 42/44 to be refracted through portions thereof forreflection from a first code scale 30 comprising data strips 33. Thefirst dome lens 60 a is further configured to permit light emitted fromthe light emitter 42/44 to be refracted through portions thereof forreflection from a second separate index scale having index strips 31. Asshown in FIG. 6 a, the first code scale 30 and the second index scaleare configured to travel along respective parallel but different thirdand fourth axes 23 and 25.

The index scale is located operably in respect of the first and seconddome lenses 60 a and 60 b such that at least a portion of the lightreflected from the index scale is directed towards the second dome lens60 b and refracted through portions thereof for detection by the indexchannel detector 20/46 b. The code scale 30 is located operably inrespect of the first and third dome lenses 60 a and 60 c such that atleast a portion of the light reflected from the code scale 30 isdirected towards the third dome lens 60 c and refracted through portionsthereof for detection by the data channel detector 24/46 c.

FIGS. 6 b-6 e show cross-sectional views of various other embodiments oftriple dome lens optical encoders of the invention, where air gaptrenches 72 are provided between the light emitter 42/44 and the firstside 56 on the one hand, and the dual track light detectors 46 b/20 and46 c/24 and the second side 58 on the other hand, Air gap trenches 72are configured to prevent or inhibit direct light rays emitted by lightemitters 42/44 from impinging directly upon the dual track lightdetectors 46 b/20 and 46 c/24. In the embodiments of FIGS. 6 c and 6 e,portions 74 are disposed on the outer surfaces of air gap trench 72,which are coated or treated to prevent or inhibit stray light rays fromimpinging upon the dual track light detectors 20 and 24. Portions 74 maybe formed, for example, by means of laser ablation, mechanical abrasion,or by disposing an appropriate optically absorptive, diffusive orscattering coating or material on the outer surfaces of air gap trenches73. Other means known to those skilled in the art for forming anoptically diffusive, absorptive or scattering portion 74 over the outersurfaces of air gap trench 72 so as to shield the light detectors 46b/20 and 46 c/24 from stray light rays are also contemplated and may beemployed. Air gap trench 72 may be formed by molding, grinding,ablation, and other methods known to those skilled in the art.

Referring now to FIG. 7 a, there are shown top plan and cross-sectionalviews of another embodiment of a triple dome lens dual track opticalencoder 15. The triple dome lens reflective optical encoder 15 comprisesa substrate 40 having a top surface 41 with opposing first side 56 andsecond side 58 separated by a first axis 57 disposed therebetween.Opposing third side 57 and fourth side 59 are separated by a second axis83 disposed therebetween, where the first axis 57 is substantiallyperpendicular to the second axis 83.

Continuing to refer to FIG. 7 a, a light emitter 42/44 is mounted on orattached to the first side 56 and configured to emit light therefrom.The light emitter 42/44 is covered by a first dome lens 60 a formedthereover and in direct contact therewith such that no air gap islocated between the light emitter 42/44 and the first dome lens 60 a. Anindex channel detector 20/49 is mounted on or attached to a first areadefined by a first overlap of the second and third sides 58 and 57. Theindex channel detector 20/49 is covered by a second dome lens 60 bformed over and in direct contact therewith such that no air gap islocated between the index channel detector 20/49 and the second domelens 60 b. At least one data channel detector 24/49 is mounted on orattached to a second area defined by a second overlap of the second andfourth sides 58 and 59. The data channel detector 24/49 is covered by athird dome lens 60 c formed over and in direct contact therewith suchthat no air gap is located between the data channel detector 24/49 andthe third dome lens 60 c.

The first dome lens 60 a is configured to permit light emitted from thelight emitter 42/44 to be refracted through portions thereof forreflection from a first code scale 30 comprising data strips 33. Thefirst dome lens 60 a is further configured to permit light emitted fromthe light emitter 42/44 to be refracted through portions thereof forreflection from a second index scale having index strips 31. As shown inFIG. 7 a, the first code scale 30 and the second index scale areconfigured to travel along respective parallel but different third andfourth axes 23 and 25. The index scale is located operably in respect ofthe first and second dome lenses 60 a and 60 b such that at least aportion of the light reflected from the index scale is directed towardsthe second dome lens 60 b and refracted through portions thereof fordetection by the index channel detector 20/49. The code scale 30 islocated operably in respect of the first and third dome lenses 60 a and60 c such that at least a portion of the light reflected from the codescale 30 is directed towards the third dome lens 60 c and refractedthrough portions thereof for detection by the data channel detector24/49.

As shown in FIGS. 7 a, 7 b and 7 c, the optically opaque light barrierlight barrier 70 is disposed between the first side 56 and the secondside 58, and is configured to prevent or inhibit direct light raysemitted by the light emitter 42/44 from impinging directly upon the dualtrack light detectors 20/49 and 24/49. The embodiment shown in FIG. 7 apermits the performance of dual track optical encoder 15 to be improved.Normally the performance of an optical encoder is affected by straylight. Such stray light reduces the image contrast of the encoder, andlimits the maximum speed or frequency that can be attained. Highperformance optical encoders are able to achieve high levels of imagecontrast and resolution. By incorporating the light barrier 70 into theoptical encoder 15, a higher performance optical encoder can beprovided. The light barrier 70 substantially blocks undesired straylight from impinging upon the light detectors 20/49 and 24/49. As aresult, the noise level of optical encoder 15 is minimized.

Referring now to FIG. 7 d, there is shown another embodiment of a dualtrack optical encoder comprising portion 74 disposed between the firstside 56 and the second side 58, which portion 74 is coated or treated toprevent or inhibit stray light rays from impinging upon the dual tracklight detectors 20/49 and 24/49. Portion 74 may be formed, for example,by means of laser ablation, mechanical abrasion, or by disposing anappropriate optically absorptive, diffusive or scattering coating ormaterial on the outer surface of the region disposed between first domelens 60 a on the one hand, and second and third dome lenses 60 b and 60c on the other hand. Other means known to those skilled in the art forforming an optically diffusive, absorptive or scattering portion 74 overthe outer surface of optical encoder 15 so as to shield the lightdetectors 20/49 and 24/49 from ray light rays are also contemplated andmay be employed.

Further as shown in FIGS. 6 a through 7 d, first, second and third domelenses 60 a, 60 b and 60 c may include at least one of a bevel 52 and aprotective protrusion disposed about a periphery thereof. As shown inFIG. 7 a, the at least one data channel light detector 24/49 and theindex channel light detector 20/49 may be disposed upon a single die, oralternatively may comprise discrete dice containing the index channellight detector 20 and the data channel light detector 24, respectively.The outer surfaces 54 a, 54 b and 54 c of first, second and third domelenses 60 a, 60 b and 60 c may be spherical, aspherical and/or biconicaccording to the particular application at hand. First, second and thirddome lenses 60 a, 60 b and 60 c are preferably formed from an opticallytransparent and moldable epoxy.

The triple dome lens reflective optical encoders shown in FIGS. 6 athrough 7 d may be configured such that data channel light detector 24comprises one light detector, at least two light detectors correspondingto A and B data channels, respectively, at least four light detectorscorresponding to A, B, A\ and B\ data channels, respectively, or anyother number of light detectors according to the particular applicationat hand. The substrate 40 may be a printed circuit board, a lead frame,or comprise plastic or a suitable polymer.

Included within the scope of the present invention are methods of makingand having made the various components, devices and systems describedherein.

The above-described embodiments should be considered as examples of thepresent invention, rather than as limiting the scope of the invention.In addition to the foregoing embodiments of the invention, review of thedetailed description and accompanying drawings will show that there areother embodiments of he invention. Accordingly, many combinations,permutations, variations and modifications of the foregoing embodimentsof the invention not set forth explicitly herein will nevertheless fallwithin the scope of the invention.

1. A triple dome lens reflective optical encoder, comprising: a printedcircuit board or lead frame substrate having a top surface with opposingfirst and second sides defined by a first axis disposed therebetween,and opposing third and fourth sides defined by a second axis disposedtherebetween, the first axis being substantially perpendicular to thesecond axis; a light emitter mounted on or attached to the first sideand configured to emit light therefrom, the light emitter being coveredby a first dome lens formed thereover and in direct contact therewithsuch that no air gap is located between the light emitter and the firstdome lens, the first lens being transfer molded directly over the lightemitter; an index channel detector mounted on or attached to a firstarea defined by a first overlap of the second and third sides, the indexchannel detector being covered by a second dome lens formed thereoverand in direct contact therewith such that no air gap is located betweenthe index channel detector and the second dome lens, the second lensbeing transfer molded directly over the index channel detector; at leastone data channel detector mounted on or attached to a second areadefined by a second overlap of the second and fourth sides, the datachannel detector being covered by a third some lens formed thereover andin direct contact therewith such that no air gap is located between thedata channel detector and the second dome lens, the data channeldetector comprising at least four light detectors corresponding to A, B,A\ and B\ data channels, respectively, the third lens being transfermolded directly over the data channel detector; an optically opaquelight barrier, air gap trench or portion disposed between the lightemitter and the first side and the second and third dome lenses on thesecond side, the light barrier, air gap trench or portion beingconfigured to prevent or inhibit direct light rays emitted by the lightemitter from impinging directly upon the index channel detector or thedata channel detector; wherein the first dome lens is configured topermit light emitted from the light source to be refracted throughportions thereof for reflection from a first code scale or code wheelcomprising data strips as well as for reflection from a second indexscale or index wheel, the first code wheel or code strip and the indexwheel or index strip being configured to travel along respectiveparallel third and fourth axes, the index scale or index wheel beinglocated operably in respect of the first and second dome lenses suchthat at least a portion of the light reflected from the index strip orindex wheel is directed towards the second dome lens and refractedthrough portions thereof for detection by the index channel detector,the code scale or code wheel being located operably in respect of thefirst and third dome lenses such that at least a portion of the lightreflected from the code strip or code wheel is directed towards thethird dome lens and refracted through portions thereof for detection bythe data channel detector, the optical encoder further being configuredto provide a first output signal corresponding to the index channel andsecond output signals corresponding to the A and B data channels, thefirst output signal having a duration less than that of the secondoutput signals.
 2. The triple dome lens reflective optical encoder ofclaim 1, wherein the at least one data channel light detector and theindex channel light detector are disposed upon separate dice.
 3. Thetriple dome lens reflective optical encoder of claim 1, wherein at leastone of the first, second and third dome lenses has a spherical,aspherical or biconic outer lens surface.
 4. The triple dome lensreflective optical encoder of claim 1, wherein an outer surface of theair gap trench is coated or treated further to prevent or inhibit directlight rays emitted by the light emitter from impinging directly upon theindex channel detector or the data channel detector.
 5. The triple domelens reflective optical encoder of claim 1, wherein the portion disposedbetween the first and second sides is coated or treated to prevent orinhibit direct light rays emitted by the light emitter from impingingdirectly upon the index channel detector or the data channel detector.6. The triple dome lens reflective optical encoder of claim 1, whereinat least one of the first, second and third dome lenses furthercomprises at least one of a bevel and a protective protrusion disposedabout a periphery thereof.
 7. The triple dome lens reflective opticalencoder of claim 1, wherein the at least one data channel light detectorand the index channel light detector are disposed upon a single die. 8.The triple dome lens reflective optical encoder of claim 1, wherein atleast one of the first, second and third dome lenses comprises a curvedouter lens surface.
 9. The triple dome lens reflective optical encoderof claim 1, wherein at least one of the first, second and third domelenses comprises epoxy.
 10. The triple dome lens reflective opticalencoder of claim 5, wherein the portion is formed by laser ablation,mechanical abrasion or by disposing an appropriate optically absorptive,diffusive or scattering coating or material thereon.
 11. The triple domelens reflective optical encoder of claim 1, wherein the optically opaquelight barrier, air gap trench or portion is configured to reducecross-talk associated with stray light originating at the light emitterand impinging on the light channel and index detectors.
 12. The tripledome lens reflective optical encoder of claim 1, wherein the indexchannel detector has a first width along the common axis that is greaterthan a second width along the common axis of each of the individuallight detectors contained within the data channel detector.